But the U.S. military’s efforts to harden itself against space-based disruption hardly end with folded-up charts, said Col. Rick Zellmann, the commander of the U.S. Army’s 1st Space Brigade.

“A lot of folks, when you say ‘degraded GPS’ or ‘contested GPS,’ immediately think about, ‘Oh, you’ve got to get back to your map-reading skills,’” he said. “But they don’t think of some of the nuanced parts of degradation of GPS and what that means.”

If an adversary were able to cut the U.S. Army off from space over a sustained time, it would force the service to adjust the entire way it fights, Zellmann said. Losing GPS and satellite communications shuts off the ability to gather intel with drones and forces troops to rely on shorter-range terrestrial radios. It means losing a lot of the precision of partially satellite-guided munitions like the Joint Direct Attack Munition, or JDAM. That means more extensive bombing campaign to provide reliable air support, which Zellman points out then requires a much larger logistical footprint to support it.

“Our force structure today is built around the assumption that we have GPS and we have satellite communications,” Zellmann said. “And we are very lethal when we have those things. But when you start taking away those combat multipliers, we need to go then back to the industrial-age Army, where you have to have three times as many people as the adversary does.”

Addressing that requires more than an analog wayfinding course. At its most ambitious, it could mean finding alternatives to space-based capabilities, like high-altitude platforms that fly like planes but offer continuous coverage like a satellite. It’s something the European Space Agency is starting to look at, and something Zellman says the Army’s Space and Missile Defense Command supports.

“We’re looking at things like: can we use airships that are flying in the near-space realm — you’re talking 60- to 80,000 feet up,” he said. “Can they provide some of the same capabilities that a satellite does today but at a cheaper cost?”

The United Kingdom is moving full steam ahead with the concept; it’s purchased several of Airbus’s solar-powered Zephyrs to provide intelligence and surveillance. The U.S. Army, on the other hand, has made more progress closer to the earth. It’s testing something called a Pseudolite — a system of ground-based pseudo-satellites that transmit signals similar to GPS. The terrestrial network is stronger, and therefore harder to manipulate or jam.

“The concept would be that you could have several of these out there and our GPS receivers would triangulate on those signals, rather than the ones in orbit, and we would kind of walk that umbrella of good GPS coverage forward as the force moved forward,” Zellmann said.

He said it’s also worth considering what tweaks could be made to existing platforms to make them more reliable and less dependent on space. Improving vehicles’ own navigation systems, for example, would help soldiers find their way even if they’re denied GPS.

“A lot of our platforms have inertial navigation systems on there … the problem with those inertial navigation systems is they drift a little over time,” Zellmann said. “And historically what we do is we sleigh them to a GPS device so that when they drift, the GPS can give them an accurate correction mid-stream and they can continue on…if you can make that inertial navigation system better, so it doesn’t drift as much, it’ll be better longer.”

Whatever the solutions may be, Zellmann says finding them is “imperative.”

By Caroline Houck // Caroline Houck is a staff correspondent at Defense One. She previously was an Atlantic Media fellow.